group travel

As a group of 20 traveling with a Swiss Rail Pass, would be experience is issues with boarding trains together? We're a little concern that all 20 of us will be able to get on the same train, although we're pretty sure we won't get in the same rail car. We would be traveling out of Engelberg and Luzern.

You won't have any problems in regular trains, although indeed you mostly wouldn't be able to all sit together if you haven't booked seats. If you board at the station where the train starts its journey, you can sit together if you be there in time. In case of cogwheel trains/cable cars/funiculars, it may happen that the group will be split because there's not that much capacity per ride. In case of post car rides I would recommend to book seats in advance, as must of them don't run frequently and capacity is limited.